As methods for collecting an object material from a solution, a distillation method utilizing difference in boiling points among chemical compounds or crystallization method utilizing the difference in solubilities among them are used.
However, the object material may be deteriorated in heating because, in these methods, an object component or other components from a mixed solution must be selectively evaporated or precipitated or crystallized. Further, large energy often becomes necessary for cooling or heating, therefore, these are unsatisfactory in the viewpoint of energy saving.
In addition, as another method, a liquid membrane separation method is known (see “Chemical Engineering Handbook, 6th revised Edition, pages 660). However, the separation method is a method utilizing difference in rates of passing through the liquid membrane between an object component and other components in a raw liquid material, for example, since a publicly known separation technique (see JP05239469 A) utilizing an emulsified membrane is a non-equilibrium separation in which an emulsion formed once is dispersed in another phase to form a multiple=emulsion, then extraction and reverse extraction are simultaneously carried out, it cannot be satisfied due to requirements of complex steps and operation conditions.